The present invention is directed to improving the performance and thermal efficiency of electric machines and, more particularly, to methods and apparatus for removing heat from stator end turns.
An electric machine is generally structured for operation as a motor and/or a generator, and may have electrical windings, for example in a rotor and/or in a stator. Such windings may include conductor wire formed as solid conductor segments or bars that are shaped to be securely held within a core, bobbin, or other structure. The conductors may be formed of copper, aluminum, or other electrically conductive material by various manufacturing operations, including casting, forging, welding, bending, heat treating, coating, jacketing, or other appropriate processes. Such conductors may be formed as individual segments that are assembled into a stator and then welded together.
The stator has a cylindrical core that secures the conductor segments of the stator windings in slots disposed around the circumference of the core. In many electric machines, the stator core is densely populated so that each angular position has several layers of conductor segments installed therein. In a densely packed stator operating at a high performance level, excessive heat may be generated in the stator windings. In some applications, heat must be actively removed to prevent it from reaching impermissible levels that may cause damage and/or reduction in performance or life of the motor. Various apparatus and methods are known for removing heat. One exemplary method includes providing the electric machine with a water jacket having fluid passages through which a cooling liquid, such as water, may be circulated to remove heat. Another exemplary method may include providing an air flow, which may be assisted with a fan, through or across the electric machine to promote cooling. A further exemplary method may include spraying or otherwise directing oil or other coolant directly onto end turns of a stator.
Rotors of electric machines may include windings, axially extending induction bars, and/or permanent magnets that generate heat. Friction, eddy currents, hysteresis losses, and other aspects of machine operation also generate heat. The aggregate heat may cause lowering of machine efficiency and output, and excessive heat may result in physical damage and mechanical problems.
Conventional electric machines are not adequately cooled. Although various structures and methods have been employed for cooling an electric machine, improvement remains desirable.